Vitamin A enhanced GE crops: potential problems

One of the forms the emotional blackmail over GE can take, in addition to 'we must have it to feed the world,' is to say that we must have it so that people in developing countries suffering from the terrible effects of, say, iron or Vitamin A deficiency can benefit from mineral or vitamin genetically-enhanced crops. According to Dr Prakash of Tuskegee University a GM rice, rich in iron which also contains vitamins, is already under development.

Quite apart from the question of whether one needs to modify the molecular basis of the world's entire food supply in order to get these specific products, the following comments on this issue from Dr Suzanne Wuerthele of the US Environmental Protection Agency indicate that such products may actually pose more of a problem than a solution. These are certainly considerations that should have been fully explored before such developments ever got started and once again expose the molecular myopia

Dr Suzanne Wuerthele of the US Environmental Protection Agency has recently commented, "...the costs, hazards and practicalities of genetically engineering a staple crop in developing countries to contain a powerful drug should be compared with the cost and ease of simply identifying deficient individuals and supplying them with Vitamin supplements, or of ensuring that the poor have access to a more nutritious diet." *** [posted to Cornell e-mail list]

About the GE rice with increased vitamin A content: While this might serve as a supplement for people with deficient diets, there are significant problems with putting a drug in entire country's staple food supply. These include quality control of the active ingredient content, and restricting access to sensitive populations.

Vitamin A is required at low doses, but it may be toxic at levels only 10 times those required to prevent deficiencies (see for example, Casarett & Doull's Toxicology, 5th ed, 1996). Hypervitaminosis A has occurred in adults who took 3-6 mg of retinol daily for 2 years. The Food & Nutrition Board of the National Research Council has warned that ingestion of more than 7.5 mg of retinol daily is ill advised. Early signs of chronic retinoid intoxication include dry and peeling skin, dermatitis, disturbed hair growth, bone pain, anorexia, edema, fatigue and hemorrhage. There are pathological changes in the liver and there may be alterations in blood chemistry which cause bone demineralization or neurological symptoms secondary to increases in intracranial pressure (see Goodman & Gilman's The Pharmacological Basis of Therapeutics, 7th Ed. 1985).

Given the low therapeutic index of Vitamin A (toxic dose divided by therapeutic dose) it would be important for a GE rice to produce consistently low concentrations of the vitamin, concentrations which would not produce toxicity when the rice is used as a staple (including high-end consumption patterns). Moreover, since GEOs have shown some tendency to be unstable, or to produce unexpected biochemical reactions, it would be important for the content of such GE rice to be monitored over time. Accomplishing such monitoring in developing countries could be problematic.

Of more concern are populations especially sensitive to the drug. Fetal exposure to excess Vitamin A results in a wide variety of birth defects, including malformation of the face, limbs, heart, central nervous system and skeleton. These occur in humans whose mothers have consumed only about 7.5 to 12 mg retinol daily during the first trimester of pregnancy. Depending on its Vitamin A content, it therefore might be advisable to restrict Vitamin A-containing rice to people who could not become pregnant. This could also be problematic in a developing country, where food shortages are common and consumer education programs are non-existant. Despite vigorous efforts of the U.S. Food & Drug Administration to educate physicians and patients, and a program to restrict the use of the anti-acne drug Accutane (13-cis-retinoid acid) to persons without childbearing potential, infants with birth defects attributable to this drug have been with born in this country.

Vitamin A occurs in animal tissues as retinol. Its precursors, which can be converted by the human liver to Vitamin A, are abundant in many vegetables, especially those containing carotenoid pigments. It would therefore seem that the costs, hazards and practicalities of genetically engineering a staple crop in developing countries to contain a powerful drug should be compared with the cost and ease of simply identifying deficient individuals and supplying them with Vitamin supplements, or of ensuring that the poor have access to a more nutritious diet. (Source: Norfolk Genetic Information Network (NGIN) [End]